PT0505. Prototype lens, calculated in 1944 (!) by GOI. Very few lenses released by GOI in 1944-1949. Focal length - 2.8 cm, aperture range f6.0 - f22. Focusing range from 1 m to infinity. Number of elements/groups: 4/4.  Angular field - 75º. Kiev (Contax) mount.

Sample opposite scanned from GOI Catalogue (1963).

PT0505 - Orion-15 prototype lens.

PT0510. Seems to be the prototype version of Orion-15 lens, released by KMZ in 1951. Signally different body finish, slightly changed the optical scheme of the lens (see picture below). Kiev (Contax) mount. 

Sample opposite from the 1st Soviet Camera Catalogue (1958).

PT0510 - Orion-15  #5100001.

PT0515. An ultra rare to find short-run preseries version of Orion-15 lens. Kiev (Contax) mount. Released by KMZ in 1955. Almost identical to PT0510, but with slightly changed markings - infinity symbol "∞" becoming bigger already, character "4" changes his form, etc. An only so far known lens has s/n #5500007 (I.Stolyar coll.).

Lens #5500007 opposite from Ilya Stolyar (USA) collection.

PT0570. Very uncommon to find version of Orion-15 camera with Kiev (Contax) mount. Small quantities released by ZOMZ in 1964-1974. 6-digits serial number, name markings in export characters. "MADE IN USSR" engravings on side-plate.

Lens #740637 opposite from Ilya Stolyar (USA) collection.

PT0570 - Orion-15  #740637.

PT0590. Home-made version of the Orion-15 lens with internal Kiev (Contax) bayonet. No otherwise different from PT0550. 

Lens #641589 opposite from Ilya Stolyar (USA) collection.

PT0590 - Orion-15  #641589.